The Musculus infraspinatus originates in the Fossa infraspinata of the shoulder blade. This is located on the outside of the bony shoulder blade. It starts at the large hump (tuberculum majus) of the humerus.
Due to this course, its main task is external rotation. In addition, it lifts the entire upper extremity outwards when the arm is raised. If the arm is lowered, the muscle infraspinatus guides the arm inwards.
Furthermore, the tendon of the muscle radiates into the joint capsule of the shoulder, thus strengthening and tensioning the capsule. The infraspinatus muscle is part of the rotator cuff and can therefore be injured and lose its function if the rotator cuff tears. The most common cause of a rotator cuff tear is years of overuse of the shoulder muscles and thus also of the infraspinatus muscle.
However, dislocation of the shoulder joint (luxation) or a strong force applied to the shoulder can also lead to a rupture of the muscles. If the infraspinatus muscle is affected, patients initially experience severe pain. In this case, the shoulder is no longer properly stabilized and assumes an unusual position.
In the case of the infraspinatus muscle, the shoulder is rotated inwards and may appear to be slightly tilted forward. This is due to the actual course of the muscle, its origin and insertion. Since the infraspinatus muscle primarily enables external rotation, the patient can only rotate the arm externally with difficulty and in severe pain.
Furthermore, the infraspinatus muscle moves the arm away from the body and also towards the body. These movements are also severely restricted by a loss of function. Other diseases, such as inflammation of the tendon or shoulder dislocations are not usually caused by the infraspinatus muscle.
